Did you know that during the last real estate bubble that nearly 20% of all the homes that exist today were built. There was probably no better time in American History and probably will not be for at least a decade or two, to take advantage of energy efficiency using high-tech building materials. Unfortunately, that residential real estate boom is over. But can we learn anything from our mistakes with regards to building more energy efficient homes?The answer is yes, but first we need to understand what happened. You see, not all homes were built without energy efficient materials or designs, but most were, as they were catering to first time home buyers who could barely afford them. What is a shame is that these inexpensive homes that saved on materials will end up costing them 5-10 times the savings during construction in higher energy costs.We had a great opportunity during the last housing boom to build more energy efficient homes and we failed, merely because it might raise the cost $500 for better doors that seal, $1200 for increased insulation costs, $1500 for super sealing windows and $3,000 for better windows. That is a smart thing to do and the ROI (return on investment) for the energy savings is less than 5-years easy.Much faster than solar and such, but we failed as builders wanted to get new home buyers in who could barely afford to buy and even those little increases might cause them not to qualify. It’s so short sided, but that is how things worked. Now the homes are already built so some things cannot be done so cheap and easy, while others like door and window weather stripping etc. can.President Obama has put forth some monies in the stimulus package to help retrofit millions of homes with better weather stripping, but it is too bad we didn’t consider all this ahead of time. Perhaps next time we will be wiser? Think on this.